Compositions for preparing cement-adhesive reinforcing fibers

ABSTRACT

A modified composition is disclosed for compounding with a polyolefin to produce a resin from which cement adherent polyolefin fibers may be produced by conventional fiber forming methods. The modifier composition comprising a polyolefin resin modified to contain a reactive Si(IV) moiety. A preferred embodiment comprises the reaction product obtained from the high shear dry blending of an alkylamino alkoxysilane with an acid modified polyolefin, preferably gamma-aminopropyltriethoxysilane dry blended with meleated polypropylene. Such modifier composition when compounded in from about 1 to about 10 weight percent with a polyolefin, preferably polypropylene, provides a resin from which cement adherent fibers may be produced.

FIELD OF THE INVENTION

This application is a continuation-in-part of our copending applicationU.S. Ser. No. 846,666 (P-1158), filed Mar. 3, 1986, now abandoned whichis turn is a continuation-in-part of copending application U.S. Ser. No.816,032 (P-1152), filed Jan. 3, 1986, now U.S. Pat. No. 4,710,540.

This invention relates to a modifier polyolefin composition containing areactive silicon (IV) group which renders polyolefins highly adherentfor silicic surfaces. When compounded with a polyolefin, the modifiercomposition of the invention provides a polyolefin resin from whichcement adherent reinforcing fibers may be prepared which suitablysubstitute for asbestos fibers as a fibrous reinforcement for cementstructures. Alternatively, the modifier composition may be applied as acoextruded surface coating to polyolefin fibers or as a surface layer toa polyolefin film from which fibers are prepared by fibrillation. Theinvention also relates to the cement adherent polyolefin fibers soprepared and to cementitious articles prepared with such cement adherentpolyolefin reinforcing fibers.

BACKGROUND OF THE INVENTION

Fibrous reinforcement is a well known method for improving the physicalproperties of cement and concrete structures. Asbestos fiber-reinforcedcements have been widely employed as building materials.Asbestos-reinforced cements and concretes have long been used for theproduction of pipes, corrugated boards, roofing slates, machinefoundations, storage tank walls, reactors, aircraft runways, roads,pilings and many other high strength articles. The type of asbestoswhich is satisfactory as fibrous reinforcement for cement is availablein limited quantities. It is probable that the deposits of such workableasbestos will be exhausted relatively soon. Further, asbestos is nowknown to have carcinogenic effects. The carcinogenic properties ofasbestos has lead to governmental regulations controlling and limitingits use.

Of the fibers currently used as an asbestos fiber replacement for cementreinforcement, polyacrylonitrile and polyvinyl alcohol fibers arepreferred because they combine high fiber strength with good adhesion toa cement matrix. Unfortunately, both are expensive materials andsignificantly increase the cost of producing fiber reinforced cementstructures.

A variety of other less-expensive materials have been considered forproduction of cement reinforcement fibers to replace asbestosfibers.Steel fibers have been tried and found inadequate because they sufferfrom chemical attack by the alkaline cement environment. Variouspolymeric fibers have also been found to be inadequate. Glass andpolyester fibers degrade due to the alkaline environment of the cementmatrix. Nylon and cellulose fibers have been found to be too watersensitive to be successfully used.

Ideally, polyolefin fibers could be employed as an asbestos replacementfor reinforced cement. Polyolefin fibers possess good inherentproperties, such as alkaline resistance, good stiffness and tensilestrengths and are relatively inexpensive. Unfortunately, a majorobstacle to the use of polyolefins as a cement reinforcing fibermaterial is their inherent lack of affinity towards an alkaline mineralmatrix. Further, polyolefin fibers are less dense than a cement slurry;that low density in combination with polyolefin's lack of affinity foraqueous systems allows polyolefin fibers to float to the slurry surface.Such poor dispersibility of polyolefin fibers results in poorreinforcement of a finished cementitious article. The inclusion in theresin formation of a dense filler such as CaCO₃, talc and the like issometimes practiced to make the fibers less buoyant and to improve theirdispersion.

Extensive efforts have been devoted to preparing polyolefin fibers,particularly polypropylene fibers, in a form which permits them to besuccessfully used as a replacement for asbestos fibers for reinforcementof cement and concrete structures.

Methods for fabricating polypropylene fibers in a way as to providephysical anchoring sites along the fibers for mechanical attachment ofthe cement matrix have been tried, as illustrated by U.S. Pat. Nos.4,261,754; 4,414,030 and 4,477,522. European Patent Application 0 026581 discloses that such fibers may be prepared by fibrillation of apolyolefin film which has been pretreated with a coupling agent such asan acid anhydride or methacryloxypropyltrimethoxysilane. Other methodsinvolve the addition of certain thickening and clay additives to thecement slurry to hold the polypropylene reinforcing fibers in dispersionuntil the slurry sets, as illustrated by U.S. Pat. Nos. 4,363,666 and4,428,775. Still another method to improve flocculation of polypropylenefibers when mixing with cement is to treat the cement-fiber mix with awater-soluble or emulsifiable polymer and a polyvalent salt such as Al₂(SO₄)₃, as illustrated by U.S. Pat. No. 4,339,273.

Other procedures designed to render polypropylene fibers suitable as acement reinforcing material involve the physical modification of thefiber surface by various means. To produce cement adherent fibers U.K.Patent Application No. 2,030,891 teaches a method for embeddinginorganic powers in the surface of fibrillated polypropylene. JapanesePatent Publication No. 60 060 960 applies a fine aggregate to the fibersurface by means of a radiation hardenably epoxy binder to produce acement adherent polypropylene reinforcing fiber.

Still other methods chemically treat the surface of polyolefin fibers torender the fiber surface more adherent to cement. Such methods includetreatment of the polyolefin fibers with an aqueous dispersion ofcolloidal alumina or silica in conjunction with a chlorinatedpolypropylene, as taught by Japanese Patent Publication No. 7319849; anon-ionic or cationic polymer agglutinating agent such as a polyethyleneoxide or poly(alkylaminoacrylate) as shown by Japanese PatentPublication No, 60 081 052; or a solution of an alkali or alkaline earthmetal (bi) carbonate as disclosed in Belgium Patent No. 899,810.

Yet others have suggested chemical modifications of the base polyolefinfrom which the fibers are produced. Hence, U.K. Patent Application No.2,021,552A states that an inorganic or organic acid group should beincorporated in the base polyolefin, either by copolymerization of acidmonomers or by grafting acid groups to a prepared polyolefin, in orderto improve the adherence to cement of fibers made of modifiedpolyolefin. Polypropylene grafted with maleic anhydride is illustratedas an example of an improved material for producing cement reinforcingfibers. Japanese Patent Publication No. 49 036 748 also illustrates theuse of maleated polypropylene as a material for producing cementreinforcing fibers. Another approach, as discussed in GermanOffenlegungsschrift DE 3341 462 Al, treats the polyolefin under elevatedtemperature and pressure with a solution of silane or SiCl₄ togetherwith silicic acid or a metal silicate and thereafter precipitates thereaction product as fibrils by lowering the temperature. The fibrils soproduced are useful as asbestos fibers substitutes for reinforced cementstructures.

Others have suggested that the surface of polyolfin fibers becatalytically reacted with reactive organic or inorganic Si (IV)compounds to render them adhesive to cement. Among the silanes disclosedas suitable for a method of this type are silicic acid anhydrides,organic halosilanes, and silicate esters as discussed in European PatentApplication No. 0 051 256 and German Offenlegungsschrift DE 32 10693 Al.

To date, polyolefin fibers have been made compatible as reinforcementfiber for cement only by incorporating additional compatibilizing agentsinto the cement slurry into which the fibers are admixed, by the specialfibrication of the fibers to provide physical anchoring sites thereinfor mechanically anchoring to the cement matrix, by the chemicalmodification of the base polyolefin from which the fibers are thenproduced, or by the chenical modification of the fiber surfaces bycostly and time consuming chemical reactions.

Ideally an agent could be found which, when admixed in small quantitieswith a polyolefin stock material, would allow the direct production ofcement adherent fibers therefrom by conventional fiber productiontechniques. To date, no such additive has been disclosed by the art.

SUMMARY OF THE INVENTION

Compositions which render polyolefins highly adherent to silicicsurfaces have been discovered which can be compounded with an olefinicpolymer to provide a polyolefin resin from which cementadherent fibersmay be directly produced by conventional fiber fabricating techniques.The compounds comprise a polyolefin linked to a highly reactive Si (IV)moiety. The compounds may be produced by melt or solution blending ofthe components or in some cases by dry blending the components. Apreferred modifier composition comprises the reaction product whichresults upon the high shear dry blending of an alkylamino alkoxysilanewith an acid modified polyolefin. A particularly preferred modifiercomposition is the dry blend reaction product ofgamma-aminopropyltriethoxysilane with a maleated polypropylene.

The preferred modifier composition may be dry blended in small amountswith an olefin homopolymer or copolymer to provide a polyolefin resinstock from which cement adherent fibers may be directly produced byconventional fiber extruding, spinning or fibrillation techniques.Alternatively, the modifier composition or a dilution thereof may becoextruded as a surface layer upon an olefin polymer film and cementadherent fibers may be produced from said film by fibrillationtechniques.

Fibers produced from a polyolefin resin which incorporates a modifiercomposition of the invention are adherent to cements and concretes andmay be used as a substitute for asbestos fibers for the fibrousreinforcement of cement and concrete articles. Polyolefin reinforcingfibers produced in accordance with the invention impart superiorstrengths to finished reinforced cement articles as compared to articlesreinforced with fibers produced only from an acid modified polyolefin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the force-displacement curve obtained upon a bending test is ahorizontal configuration of a concrete test bar reinforced with 4 volumepercent polypropylene fibers containing a modifier composition inaccordance with the invention.

FIG. 2 is the force-displacement curve obtained upon a bending test in ahorizontal configuration of a concrete test bar reinforced with 4 volumepercent polypropylene fibers not containing any modifying composition ofany type.

FIG. 3 is the force-displacement curve obtained upon a bending test in ahorizontal configuration of a concrete test bar reinforced with 4 volumepercent polypropylene fibers containing an amount of maleatedpolypropylene equal to the amount of modifier composition contained bythe fibers used in reinforce the concrete test bar of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Any polyolefin may be rendered suitable for production of cementadherent fibers by the addition thereto of a modifying agent of theinvention. Examples of suitable polyolefins are polyethylene;polypropylene; polybutene; olefinic copolymers such as ethylene-butene-1or propylene-ethylene copolymers; olefinic terpolymers such aspropylene-ethylene-butene-1 terpolymers; or mixtures and blends of theolefinic polymers. In view of its good intrinsic physical and chemicalproperties, polypropylene and its copolymers is a preferred material forthe production of concrete adhesive reinforcing fibers.

The modifying agent which is compounded with a polyolefin to render itadhesive to cement comprises a compound with the following structure:##STR1## wherein P comprises a polyolefin segment with degree ofpolymerization greater than about 50 and desirably in the range of about50 to about 1,000, preferably in the range of about 100 to about 1,000,and most preferably in the range of about 100 to about 300; is 0 or 1;R¹ is an alkylene group having from about 1 to 10 carbon atoms, aryleneor alkyl substituted arylene group having 6 to 20 carbon atoms,oligomeric siloxane group having from 1 to 10 Si atoms, alkylene amideor imide, arylene amide or imide, alkylarylene amide or imide, alkyleneor arylene sulfonyl amine, alkylene or arylene ester, alkylene orarylene carbonate with the alkylene or arylene components of theforegoing being in the ranges of 1 to 10 and 6 to 20 carbon atoms,respectively, or other linkages required to affix the silicic moiety tothe polyolefin chain. R₂, R₃ and R₄ are each independently hydrogen,halogen, hydroxyl, alkyl or alkoxy groups with the proviso that at leastone of R₂, R₃, and R₄ must be either a hydroxy, halogen, or alkoxygroup. Preferably R₂, R₃ and R₄ are each a halogen, hydroxy or an alkoxygroup. Examples of the effective compositions include: the graftcopolymer of vinyl triethoxy silane and polyethylene or polypropylene;the nitrene insertion reaction product of a trimeth- oxyazidosilane withpolypropylene or polyethylene; the condensation copolymer of3-(trimethoxysilyl)-1-propanol and maleated polypro-pylene orpolyethylene; reaction product of 3-aminopropyldimethyl-ethoxysilanewith an acid modified olefin polymer. A preferred composition of themodifier is the reaction product of an alkylamino alkoxysilane with anacid modified olefinic polymer.

The preferred modifying agent which is compounded with a polyolefin torender it adhesive to cement comprises a dry blend reaction product ofan alkylamino alkoxysilane with an acid modified olefinic polymer,copolymer or terpolymer. An alkylamino alkoxysilane is defined herein tomean a Si(IV) compound of the following structure: ##STR2## wherein R₁is an alkylene having from about 1 to about 10 carbon atoms andpreferably from about 3 to about 8 carbon atoms or an alkyl arylenegroup having from about 6 to about 20 carbon atoms, and R₂, R₃ and R₄are each independently hydrogen, alkyl or alkoxy groups with the provisothat at least one of R₂, R₃, and R₄ must be an alkoxy group and R₅ ishydrogen, alkyl, aryl or a substituted version thereof. Preferably R₂,R₃ and R₄ are each an alkoxy group. An acid modified polyolefin asdefined herein means an olefinic homopolymer, copolymer or terpolymerwhich contains from about 0.4 wt% to about 8.0 wt% acid functionalgroups as free carboxylic acid or as carboxylic acid anhydride.

Surprisingly, it has been found that the amino group of an alkylaminoalkoxysilane when mixed by high shear dry blending with an acid modifiedpolyolefin will react with the acid functionality of the modifiedpolyolefin without further requirements of a catalyst, solution orextremes of temperature. The resulting modifier composition comprises analkoxysilane amide or imide adduct of a polyolefin which, in accordancewith the invention, may inexpensively be prepared in bulk quantitieswith readily available dry blend mixing equipment.

A polyolefin resin for production of cement adherent fibers may readilybe prepared by blending the modifier composition with an olefinicpolymer. The modifier is intimately and homogeneously admixed with thebase polyolefin compound to form a resin from which fibers aresubsequently produced. Fibers produced from such modified polyolefinresin exhibit a rougher surface texture than fibers produced from apolyolefin not containing the modifier agent. This is believed to be dueto the migration of the modifier agent from the polymer matrix of thefiber core to the surface of the fiber during fiber forming or filmproduction from the resin. This migration or blooming phenomena isbelieved to account for the fact that a small amount of the modifieragent may be incorporated into a polyolefin resin yet significantlyincreased adhesion of fibers produced therefrom towards cement is stillachieved.

The acid modified polyolefins which may be employed to produce themodifier agents of the invention are those acid modified polyalpha-olefins or mixtures thereof; such as acid modified polyethylene,polypropylene, polybutuene-1, and olefinic copolymers. The acid modifiedpolyolefins are known materials and may be prepared by known procedures,as disclosed for example in U.S. Pat. No. 2,973,344. The unsaturatedalpha-beta carboxylic acids and acid anhydrides useful for forming theacid modified polyolefins are exemplified by acrylic acid, maleic acid,fumaric acid, itaconic acid, citraconic acid, methacrylic acid, crotonicacid, isocrotonic acid, maleic anhydride, itaconic anhydride, citraconicanhydride, and himic anhydride. Preferably, to insure that the modifieragent produced from such acid modified polyolefins will readily migrateor bloom to the surface of a polyolefin fiber, the polyolefin portion ofthe acid modified polyolefin used to produce the modifier desirably hasa number average molecular weight of from about 2,500 to about 50,000and desirably 2,500 to about 30,000. If the number average molecularweight of the polyolefin portion of the acid modified polyolefin exceedsabout 50,000 there is a reduction in effectiveness probably associatedwith the reduced mobility of the larger molecule. Of course, acidmodified poly-olefins having a number average molecular weight in excessof 50,000 may be used to prepare modifiers of the invention, but in suchcase it is desirable to incorporate such higher number average molecularweight modifier composition into the base polyolefin as a coextrudedlayer upon a polyolefin film from which fibers are subsequently producedby fibrillation.

Alternatively, if the acid modified polyolefin is a polyethylene, it maybe produced by the copolymerization of ethylene monomer with from about0.1 to about 8 weight percent of an acid olefin comonomer. Examples ofcopolymer suitable as the acid modified polyolefin include copolymer ofethylene with acrylic acid, methacrylic acid, itaconic acid, malonoicacid and methylmethacrylic acid.

The acid content of the acid modified polyolefin may range from about0.4 to about 8.0 weight percent. As noted, the number average molecularweight of the polyolefin component, particularly wherein the polyolefincomponent is polypropylene, would desirably be from about 2,500 to about50,000 and desirably 2,500 to about 30,000, and most desirably be fromabout 5,000 to about 10,000. The content of the acid component shouldpreferably be selected to provide on the average from one to to acidgroups per polymer chain. Although an acid modified polyolefin may beused which has an acid content which exceeds on the average two acidgroups per polymer chain, generally no significant additional benefit isobserved from the excess amount of acid component. The preferred acidmodified polyolefin is a maleic anhydride modified polypro-pylene, suchas a 5000 number average molecular weight polypropylene with an acidnumber of about 40, are marketed by Eastman Chemicals as Epolene-43.

Examples of alkylamino alkoxysilanes which may be used to prepare thepreferred modifier compositions of the invention included the classes ofalkylamino alkyldialkoxysilanes exemplified by adeltaaminoalkyl-methyldimethoxy silane anddelta-aminoalkyl-methyldiethoxysilane such asdelta-aminobutyl-methyldimethoxysilane; gamma-aminoalkyltrialkoxysilanes as exemplified by gamma-aminopropyl triethoxysilane;N-alkyl substituted gamma-aminoalkyl dialkoxysilanes such asN-ethyl-gamma-aminopropyl methyldimthoxysilane or N-alkyl substitutedgamma-amino alkyl trialkoxysilanes such asN-ethyl-gamma-aminopropyltriethoxysilane. The class of aminoalkyltrialkoxysilanes is preferred with gamma-aminopropyltriethoxysilane asthe compound of choice.

The preferred modifier composition is prepared by dry blending asuitable acid modified polyolefin, preferably in powder form, with fromabout 50 to about 150%, and preferably from about 50 to about 100% ofthe stoichiometric amount of alkylamino alkoxysilane required to reactwith the acid functionality of the acid modified polyolefin. Wherein theacid modified polyolefin is a maleated polypropylene such as Epolene-43,it is preferably blended with from about 3 to about 5 weight percent ofthe alkylamino alkoxysilane, preferably gamma-aminopropyltriethoxysilane. Dry blending is preferably performed by a high shearmixing method such as is obtained in a double-arm mixer, or a horizontalstationary cylindrical mixer. Frictional heat produced by such dryblending is sufficient to initiate the occurrence of reaction betweenthe amino functionality of the silane compound and the acidfunctionality of the acid modified polyolefin. The heat of reaction aidsin maintaining the course of the amidation or imidation reaction duringdry blending. Upon completion of the dry blending operation, it ispreferred to maintain the powder mixture at a slightly elevatedtemperature from about 30° to about 90° C., and preferably about 60° C.,for several hours to ensure the completion of reaction. Another processroute to effective compositions is the free radical initiated graftingof a silicon containing vinyl compound onto a polyethylene orpolypropylene chain. The peroxide initiated, melt phase reaction ofvinyl triethoxy silane with polyethylene or polypropylene is aparticular example.

A polyolefin resin for production of cement adherent fibers is preparedby mixing from about 2 to about 50 melt index polyolefin, such aspolypropylene, with from about 0.5 to about 5 wt% of the modifiercomposition. Preferably the polypropylene has a melt index (measured at230° C.) of from about 2 to about 10. Generally, modifier contents offrom about 1 to about 3 wt% provide the resulting polyolefin resin withadequate adhesion toward cement. The modifier may be compounded with thepolyolefin in a single-screw or twin-screw extruder of co-rotating orcounter-rotating design, extruded to strands and pelletized by a hot dieface cutting or a cold cutting system.

The pelletized modified resin may be used as the feed stock for fiberproduction by any of the conventional fiber forming methods. Filamentsof the so modified polyolefin resin may be prepared by melt-spinningtechniques or by film slitting.

If desired, the modified resin may be continuously prepared and feddirectly to the fiber forming process. The intermediate operation ofpreparing the resin in pelletized feed stock form may be omitted.Likewise, the modifier composition need not be separately prepared, butmay be formed in situ by direct compounding of the requisite quantitiesof acid modified polyolefin and alkylamino alkoxysilane with the basepolyolefin compound.

The cement adherent reinforcing fibers formed from the modifiedpolyolefin resin should be prepared as a 1 to 100 denier fiber,preferably from about 2 to about 80 denier, with the preferred fibersize being dictated by the details of the cementitious matrix. Thefibers may be prepared in any length, but lengths of from about 1/8 to 3inches are preferred, and most preferred are fiber lengths of from about1/8 to 1 inch.

Cement adherent polyolefin reinforcing fibers prepared in accordancewith the invention are suitable for reinforcement of all common cementcompositions, such as Portland cements, marble cement, puzzolaniccement, trass cement, blast furnace cement, gypsum cements, calciumsilicates and others. In addition to the reinforcing polyolefin fibersof the invention, the cement composition may contain further additivesand fillers such as fly ash, limestone, quartz, pearlite, rock wool,cellulose, diatomaceous earth, flue dust, pozzolana or mixtures thereof.

Reinforced cement articles are prepared by mixing polyolefin reinforcingfibers of the invention with the cement slurry in fiber amounts of fromabout 0.5 to about 20 percent by volume (dry basis), preferably fromabout 1 to about 10 percent by volume, and most preferably in fiberamounts from about 2 to about 8 percent by volume.

EXAMPLE 1

A modifier composition was prepared by mixing 4.5 parts by weight ofgamma-aminopropyl tri-ethoxy silane and 95.5 parts by weight of maleatedpolypropylene (Eastman Chemicals' Epolene-43, MW=5000, acid number about40) in a lab Waring blender. The resulting mix was then stored at 60° C.for several hours to allow the reaction between the anhydride and theamine to proceed to completion. Next, 1.65 parts by weight of theresulting modifier composition was blended with 98.35 parts by weight ofa 3 melt flow rate polypropylene and the blend pelletized in a smallsingle screw extruder.

The pelletized modified polypropylene resin was then extruded into film;the film was oriented, fibrillated and chopped into staple fiber ofabout 20 denier and 6 mm length. This staple was randomly dispersed in aconcrete made by mixing Portland cement type P-40, fine sand type 0000and water (according to Norm NBN B.12-208; consistency 1.5 as describedin Norm NBN B 14-207). The fiber was present in the final formulation tothe extent of 4 vol%. Test bars of 15.5 cm length, 2 cm width and 1 cmheight were molded from the concrete. The bars were cured in water andthen in a wet chamber (as per Norm NBN B.12-208).

Comparison samples were prepared by producing staple fibers in a manneridentical to that described above from an unmodified 3 melt flow ratepolypropylene and from polypropylene compounded to a resin with 1.65parts of a maleated polypropylene (Epolene-43). Concrete test barspecimens embodying the unmodified fibers were prepared in exactly theway described above.

The cured bars were then subjected to a bending test in a horizontalconfiguration with a support near each end of the bar and the loadapplied from the top in the center of the bar. The force-displacementresults are displayed in FIGS. 1, 2 and 3. FIG. 1 gives the results forthe bars reinforced with the modified polypropylene fibers of thepresent invention. FIG. 2 represents the results for the comparisonsample using unmodified polypropylene fibers as the reinforcing agent.FIG. 3 represents the result for the comparison sample using apolypropylene fiber containing an amount of maleated polypropyleneequivalent to the amount of modifier composition contained in themodified polypropylene fibers of Sample 1.

In a test of this type, the area under the force-displacement curvecorrelates directly with toughness and extensibility in actualapplication. Comparing FIGS. 1 and 2, an increase of at least 100% isseen in this critical area measurement in going from the unmodifiedfiber specimen to the material based on the fibers of the presentinvention. Comparison of FIG. 2 to FIG. 3 demonstrates that addition ofonly a maleated polypropylene to the polypropylene fiber resin actuallydecreases the adherence of such fibers for cement.

EXAMPLE 2

A modifier composition was prepared, blended with polypropylene andextruded in accordance with the procedure of Example 1. Prior toextrusion into film/fibers, the resulting modified polypropylene resinwas dry blended with a concentrate of CaCO₃ in polypropylene so that theconcentration of CaCO₃ in the final blend was about 15 wt%. Thisincreased the density of the resulting fibers and made them moredispersible in the cement slurry.

The dry blend of CaCO₃ concentrate and modified polypropylene resin wasextruded into film, oriented, fibillated and chopped into staple inaccordance with the procedure of Example 1. Cement articles werefabricated and evaluated as in Example 1. The comparison sample chosenwas a 3 MFR polypropylene compounded to a resin with 1.65 wt% of amaleated polypropylene (Epolene-43). Comparison fibers were preparedfrom this resin in a manner identical to that described above.

The results of the evaluations of these CaCO₃ filled formulations appearin FIGS. 3 and 4. FIG. 3 is the force displacement curve for the CaCO₃filled version of the modified polypropylene of the present invention.FIG. 4 represents the results for CaCO₃ filled fibers prepared from thecomparison resin which contained 1.65 wt% maleated polypropylene(Epolene-43).

As in Example 1, the area under the force-displacement curve iscritical. In the case of the cement article reinforced with the fibersof the present invention, this area is seen to be at least 100% greaterthan for the comparison samples. Thus the presence of CaCO₃ as adensifying agent does not reduce the effect of the modifier composition.

The invention has been described and disclosed with reference to variousof its particular and preferred embodiments. Upon reading andunderstanding this disclosure a person of ordinary skill in the art mayappreciate that various modifications and changes may be made in thepractice of the invention compared to the particular and preferredembodiments as described herein which do not depart from the scope andspirit of the invention as described above or claimed hereafter.

What is claimed is:
 1. A fiber reinforced cement article comprising:cement having in intimate admixture therein from about 1 to about 10percent by volume fibers composed of from about 90 to about 99 wt% of anolefinic polymer containing from about 1 wt% to about 10 wt% of amodifying agent which is the reaction product resulting from dryblending an alkylamino alkoxysilane with an acid modified polyolefin inan amount of from 50 to 150% of the stoichiometric amount required toreact with the acid functionality of the acid modified polyolefin. 2.The article of claim 1 wherein the olefinic polymer is polypropylene andthe acid modified polyolefin is maleated polypropylene.
 3. The articleof claim 1 wherein the alkylamino alkoxysilane isgamma-aminopropyltriethoxysilane.